Note: Descriptions are shown in the official language in which they were submitted.
1056706
METHOD AND APPARATUS FOR REFORMING
1ROUND DUCTS INTO RECTANGULAR DUCTS
Background of the Invention
This invention relates to rectangular thin walled
metal ducts, and to the process and apparatus used in their
manufacture.
Round, thin walled, spirally grooved metal ducts
and their method of manufacture are known as evidenced by U.S.
Patents Nos. 3,435,852 and 3,621,884. Round ducts of this type
have many uses, e.g., as cold or warm air ducts for residential,
locommercial and industrial construction. However, these round
ducts, and the method and apparatus used in their manufacture,
have certain disadvantages. Round ducts require an excessive
wall space thickness to carry the required volume of air for
many applications. In a typical interior residential wall the
space between studs will easily accept a 2 1/2" x 12" rectangular
duct which provides a cross-sectional area of 30 square inches.
A 2 lt2" diameter round duct, about the largest round duct that
will fit in this space, has a cross-sectional area of only about
2 square inches.
This emphasizes the need for rectangular ducts. The
problem is that the method and apparatus used to make the round,
thin walled spirally grooved metal ducts, as is apparent from the
above mentioned patents, will not produce rectangular or flat oval
ducts. Further, it is not apparent how this apparatus and method
could be modified to make rectangular ducts.
This situation has forced the use of conventional
straight walled galvanized metal ducts in those applications where
wall thickness dimension and duct cross-sectional area are critical.
30This type of conventional duct, usually rectangular, does not have
.,., ' ~
~i `
~05~j7~16
1 many of the features that the round, thin walled, spirally
grooved metal duct has~ e.g., the ability to be hent
around curves, etc. without significantly changing the
cross-sectional area at the bend, light weight and low
cost due to the use of aluminum and steel sheet having
a thickness of less than 10 mils and usually in the range
of 3-6 mils, a continuous spiral crimped seal, and the
ability to be made in a continuous manner from relatively
narrow strips of metal and requiring little hand labor.
Thus, the need or rectangular thin walled, spirally
grooved metal is clear.
Attempts have been made to reshape round,
thin walled, spirally grooved metal duct into rectangular
duct by external forces, but, because of the very thin
wall, the duct tends to crimp rather than be reformed
into the desired shape.
The object of the present invention is a rectan-
gular duct having the desired features of the round, thin
walled, spirally grooved metal ducts, a suitable method
for making such a product, and a practical apparatus for
use in the method.
Brief Summary of the Invention
The present invention comprises rectangular,
thin walled spirally made metal ducts that are light
weight and bendable without significantly changing the
cross-sectional area of the duct at the bend.
The present invention also comprises a method
of making the ahove described ducts-comprising reshaping
a round, thin walled~ spirally grooved metal duct into
the desired rectangular ducts by- the application of a
plurality of reforming forces simultaneously to the
interior of the round duct.
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~56706
1 The present in~ention further comprises an
apparatus for practicing the above described method
comprising two or more forming surfaces or members fox
insertion into the interior of a hollow duct, means for
supporting said forming surfaces and a surrounding hollow
duct, and means for moving said two or more forming
surfaces apart in a direction perpendicular to the axis
of the duct, while preventing any significant horizontal
movement of the forming surfaces with respect to one another.
Brief Description of the Drawings
FIG. 1 is a perspective view of a section of
rectangular duct of the present invention.
FIG. la is a partial section through a wall,
and showing a seam, in the duct shown in FIG. 1.
FIG. 2 is an elevational side view of a
preferred embodiment of the apparatus of the present
invention showing the forming members in a retracted
position, and broken along its length for illustrative
purposes.
FIG. 3 is similar to FIG. 2, but shows the
forming-members in a fully extended position.
FIG. 4 is a plan view of the apparatus shown
in FIGS. 2 and 3.
FIG. 5 is a perspective view of a portion of
the apparatus shown in FIGS. 2-4 showing the linkage
assembly joining the forming members which are in a par-
tially extended position.
FIG. 6 is a cross section of a set of forming
members in the retracted position and linkage assem`bl~
for making a rectàngular duct and shown inserted into
a round duct.
FIG. 7 is a cross section of the apparatus
shown in FIG. 6, but the forming surfaces are in an
~6)56706
1 extended poaition having reshaped the round duct to a
rectangular duct.
FIG. 8 is similar to FIG. 6, but shows
forming surfaces~ and linkage assembly suitable for
making flat/oval duct.
FIG. 9 is a perspective view of the apparatus
illustrated in FIGS. 2-7 with the forming surfaces in a
retracted position and a round duct in place ready to
be reshaped into a rectangular duct.
Detailed Description and- Preferre_ Embodiment
The preferred embodiment of the rectangular
duct of the present invention is shown in FIGS. 1 and
la. The round duct from which this rectangular duct is
made using the method and apparatus of this invention
can be made by known methods, e.g., the method disclosed
in U.S. Patent No. 3,621,884. The rectangl~lar duct shown
in FIGS. 1 and la has a thin metal wall 1, usually below
10 mils in thickness and preferably in the range of 3-
6 mils thick. m icknesses greater than 10 mils can be
O used, but usually are not required and thus merely add
to the weight and cost of the product. Depending upon
the type of metal used in the round duct, it is possible
to reduce the metal thickness to below 3 mils, at least
for small cross-sectional area duct. Typical metals
used are vinyl coated, galvanized or stainless steels
and aluminum, but round ducts of any metal capable of being
reshaped could be used.
The thin metal walls of the rectanglar duct
comprise a plurality of spiral ~rooves having valleys
2 and peaks 4. The distance hetween each 'successive
groove and the overall wall thicknes's "X" determlnes
the flexibility and strength 'of the duct. Th'e manner
of adjusting these factors to produce the desired
10567~)6
1 properties is ~ell known as disGlosed in U.5. patent Nos~
3,435,852 and 3,62I,884 thè disclosures of which are
herein incorporated b~ reference.
A continuous crimped seam 3 extends spirally
along the wall of the duct. While the crimp pattern
shown in FIG. la is preferred, round ducts having other
known crimp patterns can be used.
The preferred apparatus for reforming round
duct into rectangular or flat/oval duct is shown in
FIGS. 2-9. Referring to FIG. 2, which is an elevational
side view, the apparatus comprises a frame 6, which can
be mounted on casters for easy movement from one area
to another. Rigidly attached to the frame 6 are two
spaced apart vertical box channel guides 8 braced by
supports 10, partly broken away, and 12. Upper and
lower die supports, 14 and 16, are held in place between
the vertical guides 8 by rollers 18. These rollers allow
the upper and lower die supports 14 and 16 to move up
and down vertically along vertical guides 8. Hardened
steel wear plates (not shown) may be fastenend to the
front and back faces of the vertical guides 8 for the
rollers to run on if desired. Such a modification presents
a smooth even surface to the rollers 18 and prevents the
rollers from indenting the softer metal of the vertical
guides 8 during use of the apparatus. Hardened steel
strips 20 provide a better foundation for the rollers
18, and also provide a more even guide between the
members 14 and 16 and the vertical guides 8.
Although the vertical guides 8 are shown as
essentially s~uare or boxed channeI members (see FIG. 4),
the apparatus could be modified to use round columns,
open channel members, etc. by modifications within the
ordinary skill of the art.
10567~6
Attached to each side of the upper and lowex
die:supports.l4 and 16 are air or h~drauIic cylinde~s 22
and 24. Extension of the:rod of each of these c~lindexs
causes members 14.and 16 to move away from one another
along vertical guides 8. These cylinders are activated
in either direction by pumping fluid to either one of
lines 26 or 28 and exhausting fluid through the other of
the two lines in a known manner.
An upper die or forming member or reshaping sur-
face 30 is attached to the upper die support member 14 by
bolts 34 and a lower die or forming member or reshaping
surface 32 is attached to the lower die supporting member
16 by bolts 36. The upper die 30 and the lower die 32 are
also attached to a control rod 38 by means of pins 40 and
42, upper pivoting linkage arms 44, and lower pivoting
linkage arms 46, as shown in FIGS. 3 and 5. Control arm
38 extends between the vertical guides 8, between guide
rollers 48, and terminates at connecting end 50 located
behind guide members 8 and guide rollers 48. Attached to
the connecting ends 50 by a clevis 52 is the rod end of a
hydraulic or air cylinder 54.
When it is desired to move the upper die 30 and
lower die 32 away from one another from the retracted
position shown in FIG. 2 to the separated position shown
in FIG. 3 to practice the method of the present invention,
cylinders 22 and 24 are simultaneousl~ energized with
c~linder 54 to cauae the die support members 14 and 16
to move a~ay from one anothe~ and to cause cylinder 54
to retract its extended rod thus moving control rod 38
from right to left as viewed in FIG. 2. When this occurs
the pivoting linkage arms 44 and 46, as shb~n in FIG. 5
cause the upper die member 30 and the lower die member 32
to move away from one another at the same rate relative to the
~56706
axis of the control rod 38. Also, since the upper die
30 and the lower die 32 are rigidly attached to the
upper support member 14 and the lower support me~ber 16
respectivel~r there is no horizontal movement of the upper
and lower die members. The apparatus could be modified
to support the upper and lower die members in a pivoting
manner and with the center member 38 supported in a fixed
position, but in such a modification it would be necessary
that the horizontal movement of the upper die member be
in the same direction and at the same rate as the hori-
zontal movement of the lower die member to prevent twisting
of the duct during reshaping.
In the apparatus shown, the cylinders 22, 24,
and 54 are hydraulic cylinders and are manipulated by
a conventional electric motor driven pump and valve
assembly with fluid reservoir 56 and electrical controls
58 mounted on frame 6 which allows the apparatus to be
portable.
The apparatus is used to reshape lengths of duct
that typically are about 10 feet long thus requiring
that the upper and lower die members 30 and 32 extend
beyond the front of the die support members 14 and 16 at
least 10 feet. The weight of these die members, and the
control are 38, because of the canilever mounting, place sub-
stantial stress on the die support members 14 and 16 and on
the vertical guides 8. This stress can be eliminated
when the apparatus is not in use by a conventional jack
60. Any conventional support can be used as the jack 60,
but the jack illustrated here is pivotabl~ mounted to
the frame 6 by pin 62 and bracket 64 thus allowing the
jack 60 to pivot down out of the way ~hen the app-aratus
is being used, as ahown in FIG. 3. The jack 60 is adjust-
able in that a threaded portion 66 is adjustably threaded
~L~S6706
into the main jack member 68 by rotation of a handle 70.
As best shown in FIG. 5, the upper and lower
die members 3Q and 32 are machined out at the proper
intervals along the interior face of the dies to pro-
vide indentations 72 into which the linkage arms 44
and 46 can fit when the dies and linkage assembly is
in a retracted position as shown in FIG. 2. These
features are critical because it is necessary that the
dies and linkage assembly can retract to a very compact
state in order that a relatively small diameter round
duct can be slipped over the dies and linkage assembly
in order to make relatively small rectangular duct. In
the embodiment illustrated here, the linkage arms form
an angle of about 14 with the axis of the control rod
38 when the dies are in a fully retracted position, but
a larger angle is preferable.
As shown in FIG. 5 the control rod 38 in the
present apparatus is comprised of two arms 76 and 78
held together by spacers 42 and screws 39 which are
threaded into the ends of the spacers 42.
As shown in FIGS. 6 and 7 upper and lower
linkage arms 44 and 46 are pivotly attached to upper and
lower die members 30 and 32 by pins 40. The pins 40 can
be fixed to the upper and lower die members 30 and 32 by
set screws that tighten against pins 40 in a conventional
manner (not shown). In the e~odiment shown in FIGS. 6
and 7 the lower linkage arm is made in the form of a
clevis at the end connected to pin 80 and thus pivots
around the upper linkage arm 44 on pin 80. The clevis
is machined out sufficiently to provide clearance for
upper linkage arm 44 so that the dies can be fully
retracted. These upper and lower linkage arms 44 and 46
1~567016
1 are also pivotly attached between arms 76 and 78 by pin
80 about Which the linkage arms 44 and 46 piVot as the
dies 30 and 32 are moved apart or retracted. The pins
80 can be fixed to axms 76 and 78 b~ set screws that
tighten against the pins in conventional manner (not
shown) or retained by other suitable fastening devices,
e.g. "D" shaped washers.
The apparatus of the present invention can
also be used to form other shapes from round duct, e.g.
flat/oval duct, by modifying the upper and lower die
members as shown in FIG . 8. The assembly shown in FIG . 8
is identical to the assembly shown in FIG. 6 except for
the shape of the upper and lower die members, thus the
elements are numbered similarly with the exception of the
suffix "a" following the element numbers in FIG. 8. The
rectangular duct of the present invention is preferred
- over a flat/oval duct that would be made using an assembly
shown in FIG. 8 because the cross-sectional area of a
rectangular duct would be greater for the same width or
thickness dimension than that of a flat/oval duct.
- In the operation of the apparatus disclosed
according to the method of the present invention to make
the rectangular duct of the present invention, reference
is made to FIGS. 5-7 and 9. Referring first to FIG. 9
jack 60 is lowered out of the way and a round duct A is
slipped over the upper and lower dies 30 and 32. To
make a rectangular duct measuring 8" x 3 1/4" a round
duct having an I.D. of about 7" would be used. C~linders
22~ 24, and 54 are then energized in such a manner to
move upper die support member 14 upwardl~, lower die
support member 16 downwardl~,and control rod 38 from
left to right as viewed in FIGS. 5 and 9, (also see the
~ OSG7016
1 arro~s showing the directions of movement of the various
members in FIG. 5). m is movement is` continued until
the forming surfaces of the upper and lower die members
30 and 32 are in the desired position to reshape the
round duct A to the rectangular shape B shown in FIG. 7.
Preferably, the upper and lower dies 30 and 32 are
moved slightly farther apart ts cause the metal of the
duct to yield slightly to remove excessive bowing and
insure straight sides on the rectangular duct after the
upper and lower dies are retracted. Having reached that
point, the upper and lower dies are retracted back to
their position shown in FIG. 6 and the rectangular duct
B is removed. The maximum size of rectangular duct that
can be made without modifyiny the apparatus will depend
upon the length of the linkage arms 44 and 46. The mini-
mum size duct that can be made will depend upon the com-
pactness of the retracted upper and lower die and linkage
arm assembly. Various size ducts can be made on the same
apparatus by varying the amount that the control arm 38
is moved horizontally. Also, wider upper and lower dies
30 and 32 can be used, e.g., by placing wider saddle mem-
bers over existing upper and lower dies 30 and 32 to make
wider or thicker rectangular ducts without changing any
of the other parts of the apparatus.
Although`the apparatus is shown mounted hori-
zontally on frame 6, it would also be mounted vertically
with the upper and lower dies and control rod hanging
vertically do~n~ard or extending vertically upward. Also,
instead of moving the round duct onto, and the rectangular
duct off of, an apparatus maintained in a fixed position,
the duct could be maintained in a fixed position and the
apparatus could be moved forward and backward, or up and
down.
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10567'06
1 In des,cribing the invention certain embodi-
ment~ have been used to illustrate the invention and
the practice thereof. Hbwever, the invention is not
limited to these specific embodiments as other embodi-
ments and modifications within the spirit of the
invention will readily occur to those skilled in the
art of reading this specification, The invention is
not intended to be limited to the specific embodiments
disclosed, but instead is to be limited only by the
claims appended hereto.
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